1. Technical Field
The present invention relates to a tire pressure monitoring system, and more particularly, to a system for reminding the vehicle operator to maintain the spare tire.
2. Background of Invention
Various types of pressure sensing systems for monitoring the pressure within the tires of an automotive vehicle have been proposed. Such systems generate a pressure signal using an electromagnetic (EM) signal, which is transmitted to a receiver. The pressure signal corresponds to the pressure within the tire. When the tire pressure drops below a predetermined pressure, an indicator is used to signal the vehicle operator of the low pressure.
Such systems, however, may not provide a separate sensor for the spare tire. Also, transmissions from a spare tire may not be constantly received due to the packaging location. That is, an RF based system may not operate in the spare tire location. One way in which to provide a reminder is to provide a reminder to the vehicle operator after a predetermined number of miles such as in the case of an oil change reminder system. However, such systems do not reflect real world conditions and therefore are most likely to be inaccurate. If a reminder reminds too much and the tire does not need air, a vehicle operator is inclined to disregard such warning signals.
It is therefore desirable to provide an accurate reminder for the vehicle operator to check the spare tire pressure.
The present invention provides for timely reminding the vehicle operator to check the spare tire pressure.
In one aspect of the invention, a tire pressure monitoring system for a spare tire of a vehicle includes an indicator and a timer that generates a first time signal corresponding to the time the spare tire is used as a rolling tire and a second time signal corresponding to a time the spare tire is stowed. The temperature sensor generates a temperature profile and a controller that is coupled to the indicator, the timer, and the temperature sensor generates a spare tire warning signal in response to the temperature profile, the first time signal, and the second time signal.
In a further aspect of the invention, a method for operating a tire pressure monitoring system for a spare tire of a vehicle comprises: generating a distance signal corresponding to the distance the spare tire is used as a rolling tire; generating a time signal corresponding to a time the spare tire is stowed; generating an ambient temperature signal; determining a temperature profile from the ambient temperature signal; generating a spare tire warning signal in response to the temperature profile, the distance signal and the time signal.
One advantage of the invention is that a separate low frequency initiator is not required for the spare tire. This reduces the cost of implementation for the system.
Other advantages and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.